import("glib3.rr")$ Cfep_loaded=0$ Glib_math_coordinate=1$ /* {{d} \over {dt}} y + 2 y = 0 , y(0)=1 plot(exp(-2*t),[400,400],[t,0,10]); */ def un() { glib_window(0,-5,10,5); glib_clear(); glib_line(0,0,10,0); glib_line(0,-10,0,10); X1 = 1.0; Dt = 0.01; T = 0.0; X2 = 1.0-2*Dt; while (T<50) { X3 = X1 - 4*Dt*X2; glib_line(T,X1,T+Dt,X2); print("[Time, (approx sol)-(true sol)] : ",0); print([T,X1-deval(exp(-2*deval(T)))]); T=T+Dt; X1=X2; X2=X3; if (X3 > 100 || X3 < -100) { print("The solution is blown up."); break; } } } un()$ end$